


Of Muscles, Origins, Insertions, and Actions

by platinumpair



Category: One Piece
Genre: Anatomy, M/M
Language: English
Status: Completed
Published: 2015-09-26
Updated: 2015-10-21
Packaged: 2018-04-23 10:08:08
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,573
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4872772
Author URL: https://archiveofourown.org/users/platinumpair/pseuds/platinumpair
Summary: <blockquote class="userstuff">
              <p>Sanji and Zoro have an exam on the forelimbs and hindlimbs of a cat.  This is how they study.</p><p>This is completely ridiculous and how I thought I would attempt to study for my exam.  You don't need to read it.</p>
            </blockquote>





	1. Hindlimb and Forelimb

Sanji lies in bed staring blankly at the ceiling. “What’s the muscle that originates from the lateral surface of the ventral border of the latissimus dorsi?” 

“Pretty sure it’s the epitrochlearis. It’s one of those muscles that inserts into the olecranon process of the ulna.” Zoro chucks the anatomy book at the blond making sure to extend his forearm with his triceps.

“How the hell am I supposed to remember all of these in time for the practical. Okay, so what supinates the hand and flexes the antibrachium?”

“Biceps brachii. It comes from the bicipital groove of the humerus and goes into the radial tuberosity near the top of your radius. You’d know if you ever used those tiny arm muscles.”

He just wants to knock the smirk off of Zoro’s face but he can’t afford it. This idiot knows his forelimbs.

“Brachioradialis. That comes from the lateral supracondylar ridge of the humerus. Where does it insert?”

“The distal styloid process of the radius. It’s another forearm flexor at the elbow. The styloid is opposite of where your wrist bone is.”

Sanji starts flexing his hands that are cramping up from all the writing he’s been doing. Zoro asks, “What muscles are you using right now?”

“Uhh, the flexor carpi radialis and ulnaris. The radialis abducts and the ulnaris adducts.” 

“They both have the same origin and insertion of the medial condyle of the humerus and metacarpals-“

“But the ulnaris also originates from the olecranon process of the ulna and pistiform bones! The pisiform bones are also carpals.” Sanji smiles at him and they continue on with the extensors. “Extensors are always on the side of the arm with the arm hair, isn’t it?”

He glances at Zoro who’s slowly moving his arm out of view. He jumps off the bed and extends his wrist to catch Zoro before he can escape Sanji. “You’re hairless! How?”

“If you tell me all the extenders in the forearm, I’ll tell you.”

“Extensor carpi radialis longus, brevis, lateralis, and ulnaris. Only the longus originates from the lateral supracondylar ridge of the humerus. Everything else originates from the epicondyle. They go into the metacarpals and extend the wrist. Now tell me why you’re a hairless rat.” Sanji loosens the grip on his forearm.

“Pretty sure it’s just genetic. My parents didn’t have much body hair either. I would have been a perfect candidate for the swim team.” Zoro pulls out the stool from underneath his desk and Sanji sits himself down along with the rest of his papers. “Okay what’s next?”

“The triceps brachii, long, lateral, and medial. I know they all insert into the olecranon process of the ulna and extend the forearm. They’ve all got different origins though.”

Zoro opens up the textbook and starts to look for some figures. He’s got his fingers between a couple pages so Sanji assumes they’re looking at a couple of different spots. “Okay, the long head originates from the axilary border of the scapula which is below the glenoid fossa and the lateral head is at the proximal point of the deltoid ridge.”

“Basically it’s the upper shaft of the humerus.” Zoro nods continuing with his explanation. 

“Now the medial has two heads. The dorsomedial surface of the humerus and the medial surface of the supracondylar foreman. It’s the hole that you can see in the humerus.”

“We’ve got three more and I’m gonna make dinner.” Sanji is just about ready to burn the book as fuel for their pasta later. “Brachialis is a forearm flexor. It comes from the lateral surface of the humerus and inserts medially on the ulna’s surface below the semilunar arch.”

“Did you remember that one?”

“Nah, I’m just reading it word for word from the packet he gave us. It’s behind the biceps brachii.”

“What muscle adducts the humerus?” Zoro performs the motion for added emphasis.

Sanji has to look away because he thinks he can actually fucking see the muscle. “The coracobrachialis. It comes from the coracoid process of the scapula and inserts into the medial shaft of the humerus. I think of the humerus like your dick. Medial is the inside part closer to your thigh and lateral surface is closer to your other thigh. Somehow it works.”

Zoro chokes on nothing. There’s a blush creeping across his cheeks that he turns away to hide. “Last one. The supinator that supinates the arm.”

“It originates on the supinator crest of the ulna and the lateral epicondyle of the humerus. I believe it inserts into the radial tuberosity.” 

“Do you know where the supinator crest is?” Zoro brushes small strands out of his face.

“It’s where the radius kind of lies in?”

“Close enough. I’m starving. Do we have any sausage for that pasta?” 

———————

Zoro likes studying with Sanji. Not just because he actually does like Sanji that way and seeing his bangs fall over his eyes is extremely sexy. They both seem to know exactly what the other doesn’t. They fill each other’s holes. Sanji’s about to teach him the leg muscles and he tends to get very physical teaching.

He almost drops his water bottle when he steps into the room. Sanji’s just got on his compression shorts. It’s gonna be a while before they can go on a run together.

Sanji sits on the desk and spreads his legs. He’s pointing at the top of his pale inner thigh. “What muscle originates from the anterior superior iliac spine of the pelvis?”

“The sartorius. It inserts into the upper tibia. Flexes, abducts and laterally rotates the hip.”

“Good now how about the muscle next to that? The one that adducts and medially rotates the hip and inserts in the same spot.”

Why does he even let Sanji tease him like this? “It’s the gracilis that comes from the ischiopubic ramus.”

“I have absolutely no clue how to demonstrate the vastus lateralis origin but it does insert into the patella.” Sanji extends his leg out and feels around for the muscle. “Just remember that it originates from the greater trochanter of the femur”

“Are you going to take off your shorts to teach me this one?” Zoro smirks. But it quickly disappears when Sanji starts pulling his waistband down over his hips. “How is this effective?”

“You’re never going to forget what my ass looks like. Now gluteus medius and maximus.” Sanji puts his lithe fingers on the pert behind. 

“They both originate on the gluteal surface of the ilium. The medius inserts into the greater trochanter of the femur while the maximus is at the gluteal tuberosity.”

“When I kick someone’s ass, my medius is abducting the hip and I can rotate laterally my thigh. The maximus rotates and extends the hip.”

“Your ass can’t be real right?”

“Come to the gym on wednesdays and thursdays after 10 and you’ll know. Let’s move on.” Sanji pulls his shorts back up and just points to an area next to his maximus. “What’s this?”

“The tensor fasciae latae. It’s a triangle that comes from the iliac crest and connects into the illiobtibal tract which is a tendon of sorts.”

Sanji runs his hand up and down his outer thigh flexing his knee at the same time. “So, how about the biceps femoris?”

“It comes from the ischium tuberosity, linea aspera of the femur. And inserts into the head of the fibula.”

Zoro’s barely ready for it when Sanji holds his ankle, extends his foot, and he’s gifted with a direct view of the back of Sanji’s calf.

“Your gastrocnemius originates from both of your condyles. It’s a knee flexor that attaches to the achilles tendon. I don’t really care for the scientific name.”

“Calcaneus, marimo. You never know if they’ll ask it or not. Now what else attaches to the achilles tendon.”

After a moment’s pause he says, “The soleus. Except it originates from the lateral surface of the head and proximal point of the ventral border of the fibula. So it’s a little lower downward.”

He starts to extend his toes. “This is the extensor digitorum longus or the EDL. It’s on the lateral epicondyle of the femur. And attaches to every toe tendon but the big one.”

Sanji lets go on his ankle flexes his foot upward. “What muscle am I using?”

“The tibialis anterior. It’s on the lateral shaft of the fibula and the head of the fibula. These ones are weird. Because you could also be using your peroneus longus. Since that originates from the head and lateral surface of the shaft of the fibula.” 

“You’re technically right on both accounts. Now where do they insert?”

“Into the metatarsals. But only the 1st one and the 5th one for the peroneus longus.”

Sanji stretches out on the table so that Zoro can get a better view of the actions of the deeper thigh muscles.

“This one you can’t really see even if you cut into me but imagine that you can.” Sanji’s pointing at his inner thigh and Zoro needs to take a deep breath. “Which muscle am I talking about?”

“Your pectineus. It starts at the pectineal line of the pubic bone and end at the pectinal line of the femur. It flexes the thigh. Now please close your thighs. I’m mildly turned on by this study session.”

“Too bad. You’ve still got two more adductors to go through.” Sanji opens them wider as if that was actually possible. Zoro would very much like to test how far back they can go later. “The longus and the femoris?”

“They both insert into the linea aspera of the femur. The longus is in the pubic bone and adducts your skinny hips.”

“Oi!”

Zoro narrowly avoids the kick aimed at his stomach. “The femoris is on the inferior ramus and also laterally rotates your thigh.”

“What are three muscles that insert into your patella?”

“Rectus femoris, vastus medialis, and the vastus intermedialis.”

“How about their origins in order?”

“The rectus is in the anterior inferior iliac spine, medialis is medial on the femur and intermedialis is on the anterolateral.”

“How are you going to remember their actions?”

“The rectus extends the knee and flexes the hip while both vastus extends the lower leg.”

Zoro takes advantage of Sanji’s position to run his rough fingers along the most medial part of Sanji’s thigh. “What are these muscles that extend your hip and flex your knee?”

“The semimenbranosus and semitendinosus. They’re both in the ischial tuberosity and insert into the tibia.”

“There’s a difference. Membranous medial condyle of the tibia and tendinousus is in the upper tibia.” Zoro pulls his fingers away to move back but is stopped by strong ankles.

Sanji pulls Zoro in-between his legs so that their crotches are flush against each other. He flexes his toes against the back of Zoro’s thighs. “So what muscles are turning you on?”

“Maybe your dick but how about the flexor digitorum longus and hallucis longus?”

Sanji drawls quietly in in his ear. “The digitorum comes from the head of fibula and the shaft of the tibia. And the hallucis starts in the shafts of the tibia and fibula.”

“Where do they insert?

“They insert into the tendons of each other.” Zoro completely loses it. He’s 90% sure that they’re both not going to walk out of this exam unaroused.


	2. Where Sanji Gets to Feel Zoro's Rectus Abdominis

**Summary for the Chapter:**

> Sanji feels Zoro's abs and they don't get as personal this time.

“Pretty sure that I fucking hate this class. I’m not even a science major.” Sanji throws his bag onto the couch adducting his arm with the pectoantebrachialis. “Don’t tell me. It originates from the manubrium of the sternum and inserts at the proximal end of the ulna.”

“We don’t actually have this muscle though. It’s just in cats.”

“Where is the pectoralis major that flexes and extends the humerus?” Zoro hints at his collarbone.

“I know it inserts into the bicipital groove of the humerus and originates from the clavicular head.”

“Now we’re onto rib cage origins. This muscle stabilizes the scapula and raises the ribs during inspiration.”

“It’s the pectoralis minor that comes from the 3rd to 5th ribs and inserts into the coracoid process of the scapula. It’s the hook thing that is where the clavicle joins at.”

Sanji contralaterally rotates his torso using his external obliques which originated from the 5th to 12th ribs. “Where does the external obliques insert? There’s three points like those earrings you have.”

“The iliac crest, pubic tubercle, and lines alba.” Zoro replies smugly. “Where’s the clavotrapezius?”

“I know it originates from the lambdoidal ridge of the skull and inserts into the raphe of the clavicle. You know our professor doesn’t even really know where that is? He keeps pointing somewhere in the medial end of the clavicle.”

Zoro flexes his forearm, turns his head and extends his humerus forward to show the action.

“What originates from C2 to T1-4 and inserts into the metacromion and scapula spine?”

“The acromiotrapezius that will draw your scapula together medially. It’s like when you wake up in the morning and get that crick out of your back.”

“Maybe because you’re getting old there cook. Now what draws the scapula dorsally?  
“Don’t tell me. It’s the spinotrapezius. T1-4 to T11-13? And it inserts into the scapular spine which is the dividing line between two muscles but we don’t ned to talk about that yet.”

Zoro pulls off the sweaty shirt to reveal his latissimus dorsi muscles which moved as he pulled his humerus caudodorsally. “Give me origin and insertion.”

“They’re in T4-5 to L6 and insert on the medial shaft of the humerus.” Sanji raises his eyes brows when Zoro rolls his eyes. “Ah, that reference.”

“What draws your scapula cranially and inserts into the metacromion of the scapula?”

“The levator scapulae ventralis originates from the transverse process of the atlas and the occipital bone.”

Sanji's getting really sick of these muscles and bones. He has two cooking practicals in the same week but they're not horrid. The next two muscles are practically the same and if he thinks of the name he can probably get them right.

"The acromiodeltoid and spinodeltoid both extend and rotate the humerus. They also insert into the deltoid ridge of the humerus. The only difference is that the aromiodeltoid inserts into the outer surface of the spinodeltoid and the branchialis anticus."

"Did you figure out how to remember their origins?"

"You've just gotta know that they originate from the scapula. And then from there you know that one is the acromion and the other is the spine."

"Do you ever wonder why one muscle can do so many things?"

"Are you talking about the clavodeltoid? That's because of it's location and how it originates from the raphe of the clavicle and inserts into the ulna under the semilunar notch. Please perform it's functions for me."

Zoro extends his humerus and flexes his forearm. He turns his head to Sanji slowly, so slowly that he can see the muscle twisting. "Your turn cook, where's the teres major and what does it do?"

"How do you go about being sexy while adducting your humerus? Forget I said anything, it comes from the inferior angle of the scapula and inserts into the intertubercular sulcus of the humerus. Pretty sure that I have no fucking idea what I just said."

"What's the muscle underneath the scapular in the subscapular fossa that medially rotates the humerus?"

"That would be the subscapularis. And it's in the lesser tubercle of the humerus."

"I'm gonna take a shower. I smell like the gym." Zoro had never put his shirt back on and just pulled his shorts off right there to chuck them at Sanji. "I'll let you feel my rectus abdominis later."

\-------

It's Sanji's turn to be mildly excited for an anatomy review session because there's probably no one he knows with torso muscles as toned as Zoro's. They start with the xiphihumeralis that originates from the xiphoid process of the sternum and inserts into the humerus.

"Can you just sit on the table? I don't feel like squatting down to look at your abs. Don't you even start. I have abs."

Zoro laughs and hops on their kitchen counter. Sanji makes a note to lysol it later. "Okay, so internal obliques and the tansversus abdominis both compress the abdomen, but the internals also rotate the vertebral column. And they originate from the iliac crest. Do you remember where that is?"

"I can visualize it but it's the part of your hip that you can feel right? Both insert into the linea alba but the transversus also inserts into the xiphoid process of the sternum." Sanji presses on the lowest part of Zoro's sternum.

"This is the part where you get to feel my godly rectus abdominis."

"Oh, shut up. Do you fucking have 8 abs?"

"It originates from the crest of the pubic bone and inserts into the 5th and 7th ribs and the xiphoid process. It flexes the lumbar spine. So your lower back if you have trouble remembering it."

"Come over here you bag of bones. And shirt off."

"Why... oh the erectorae spinae. That goes fromspinous processes of T9-12 and inserts into T1 and 2." Sanji straightens out his back for Zoro to see just how long his torso is.

"Wait, can you stand up straight again? We'll do the scalenus and external intercostals. The scalenus elevates your fist and second ribs which inserts where as well. It originates from the cervical vertebrae."

"If I breathe in, you can see my ribcage, right? And that's where the external intercostals are. They come from the lower border of the ribs and insert into the upper boarder of the posterior rib."

"You can put your shirt back on."

"You didn't need to tell me." Sanji pokes his head through the hole of the thin black shirt.

"Time for the rhomboideus major and minor that draws the vertebral border of the scapula medially and dorsally."

"It originates from the spines of T1-4. The minor inserts into the vertebral border of the scapula and the major is at the inferior angle."

"What about the capitis which draws the dorsal border of the scapula forward?"

Sanji feels around on his back. "I think it originates from the lamboidal ridge of the skull and inserts into the vertebral border of the scapula where the minor does as well."

Zoro extends his arm again and then flexes it to show the action of the supraspinatus and infraspinatus. "They originate from their respective fossa of the scapula. You get to name the insertions."

"They're both on the greater tuberosity of the humerus but the infra is on the lateral part."

"We've got one last one and we're done with the trunk. What muscle is underneath of the clavotrapezius and originates from the spinous processes of the cervical vertebrae?"

"That would be the splenius that inserts into the mastoid process of the temporal and occipital bones. It extends, rotates and laterally flexes the head."

\-----

“I’m not sure if I’m going to have to punch you in the neck or something in order to learn these muscles.”

“Let’s just use the person with the longer neck. Which so happens to be me.” Sanji straightens out his neck for easy viewing.

“First one up is the sternomastoid that turns the head, and depresses the head and neck. Whatever the fuck that means.”

“It starts at the manubrium of the sternum and goes into the mastoid process and lambdoidal ridge. Those are places in the skull that we have yet to learn.”

“Now if you go more to the center of the neck you’ll see the sternohyoid which draws the hyoid caudally.”

Sanji pokes around at the middle of his neck. “It originates from the first costal cartilage and inserts into the body of the hyoid.”

Zoro leans forward, takes two fingers, and pushes Sanji’s chin upwards to show the digastrics that depress the mandible. “Origin and insertion?”

“Ummm, the jugular process of the occipital and the mastoid process of temporal and it inserts into the ventral border of the mandible. Can you let go?”

“Only if you tell me what inserts into the median raphe and originates from the medial surface of the mandible.”

“It’s the myohyloid and it raises the floor of the mouth to draw the hyoid back. Are we almost done yet? I still have to make dinner.”

“These two muscles elevate your mandible.”

“The masseter and the temporalis! But that’s pretty much the only thing that’s similar about them. Oh, wait, they do both insert into the mandible. The masseter is in the ventral border and the carotid fossa, and the other is in the coronoid process.”

“We’re getting there. The ventral border of the zygomatic arch is where the masseter originates and the temporal fossa of the parietal, squamosal, and frontal is where the temporalis originates.”

“Where exactly is the raphe of the clavicle? Is it that part that sticks out and where the cleidomastoid also inserts into?”

“Pretty much. It originates from the mastoid process of the temporal and rotates your head. And now we’ve got the sternothyroid that depresses the thyroid.”

“I know that comes from the manubrium of the sternum and I think inserts into the thyroid cartilage.”

“If that one depresses your thyroid, then what elevates it?”

“The thyrohyoid! It starts from the thyroid cartilage and inserts into the hyoid bone. Done! We are finally done.”

**Author's Note:**

> I'll actually probably make one for each of my exams. I remember fan fiction dialogue so much better than when it's in a chart on paper.


End file.
